1. Technical Field
The present invention relates to an image recording apparatus which discharges liquid from a discharge head and records an image on a recording medium supported on an outer surface of a rotating drum. In particular, the invention relates to a technique for cooling the rotating drum.
2. Related Art
U.S. Pat. No. 5,502,476 describes a printer which discharges an ink from a print head onto an outer surface of a drum to record an image. The printer prints an image on a print medium by cooling and curing ink deposited on the drum by using the drum and transferring the ink to a print medium that forms a nip with the drum. Moreover, in order to effectively cool the ink by using the drum, the drum is cooled by air flow generated using a fan. Specifically, a fan facing the hollow portion of the drum in the axial direction of the drum generates an air flow that passes through the hollow portion of the drum in the axial direction, whereby the drum is cooled (FIG. 11).
There is an image recording apparatus which records an image on the recording medium by discharging liquid from a discharge head onto a recording medium which is guided around an outer surface of a cylindrical platen (a rotating drum). In such an image recording apparatus, when the rotating drum is heated by the heat source in the apparatus, the rotating drum thermally expands, which causes the gap between the rotating drum and the discharge head to vary, which in turn may cause the liquid to become misaligned on the recording medium. Thus, the technique of U.S. Pat. No. 5,502,476 is used to cool the rotating drum by using a fan.
However, in order to effectively cool the rotating drum by using a fan, it is required that a large amount of high-speed air flow generated by the fan passes through the hollow portion of the rotating drum to promote heat exchange between the air flow and the rotating drum. In contrast, in an image forming apparatus of U.S. Pat. No. 5,502,476, a plurality of arms are disposed radially from the rotation axis of the rotating drum in the hollow portion of the rotating drum to support an outer peripheral member (a rim) of the rotating drum. Therefore, when the rotating drum rotates in order to transport the recording medium, the arms also rotate. The rotation direction of the arms intersects (is substantially orthogonal to) the direction of the air flow, so that the rotating arms catch the air flow and stop the air flow from passing. Under these circumstances, it is not always easy to generate a large amount of high-speed air flow that is intended to pass through the hollow portion of the rotating drum and it can be difficult to efficiently cool the rotating drum.